Stannous fluoride has been used in oral care products since the early 1950's, and stannous fluoride has been reported to be an effective agent for treating various oral conditions and diseases including plaque, gingivitis, sensitivity, enamel decalcification, and periodontitis, among others. Product stability is an outstanding problem because stannous fluoride is unstable in water and forms stannous oxy-fluoride and stannic compounds, both of which reduce or inhibit enamel fluoridation, that is, formation of stannous fluorophosphate and fluoroapatite. This instability has required formulation of home treatment gels as anhydrous gels. Despite highly specialized precautionary measures during formulation of oral care products, significant variations are found in stannous ion concentrations of commercial dentifrice gel products among different manufacturers as well as among batches of the same brand of dentifrice because of stannous ion instability.